Open MPI logo

Open MPI Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Development mailing list

Subject: Re: [OMPI devel] RFC: System V Shared Memory for Open MPI
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2010-06-02 13:40:42


Don't forget that the RML is also used to broadcast the success/failure of the creation of the shared memory segment.

If the RML goes away, be sure that you can still determine that without hanging.

Personally, I still don't see the problem with using the RML stuff...

On Jun 2, 2010, at 1:07 PM, Samuel K. Gutierrez wrote:

> Hi George,
>
> That may work - I'll try it.
>
> Thanks!
>
> --
> Samuel K. Gutierrez
> Los Alamos National Laboratory
>
> On Jun 2, 2010, at 10:59 AM, George Bosilca wrote:
>
> > How about ftok ? The init function takes a file_name as argument,
> > and this file name is unique per instance of the shared memory
> > region we want to create. We can use this file name with ftok to
> > create a unique key_t that can be used by shmget to retrieve the
> > shared memory identifier.
> >
> > george.
> >
> > On Jun 2, 2010, at 11:53 , Samuel K. Gutierrez wrote:
> >
> >> On Jun 2, 2010, at 8:49 AM, Jeff Squyres wrote:
> >>
> >>> On Jun 2, 2010, at 10:44 AM, George Bosilca wrote:
> >>>
> >>>>> Not sure what you mean here. common/sm may create new shmem
> >>>>> segments at any time (e.g., during coll sm). The RML message
> >>>>> exchange is to ensure that only 1 process creates and
> >>>>> initializes the segment and then all the others just attach to it.
> >>>>
> >>>> Absolutely not! The RML messaging is not about initializing the
> >>>> shared memory segment. As stated on my original text it has only
> >>>> one purpose: to ensure the file used by mmap is created
> >>>> atomically. The code for Windows do not exchange any RML messages
> >>>> as the function to allocate the shared memory region provided by
> >>>> the OS is atomic (exactly as the sysv one).
> >>>
> >>> I thought that Sam said that it was important that only 1 process
> >>> shmctl/IPC_RMID...?
> >>
> >> Hi George,
> >>
> >> We are using RML messaging in the sysv code to exchange the shared
> >> memory ID (generated by exactly one process). I'm not sure how we
> >> would go about passing along the shared memory ID without RML, but
> >> any ideas are greatly appreciated.
> >>
> >> Thanks,
> >> --
> >> Samuel K. Gutierrez
> >> Los Alamos National Laboratory
> >>
> >>>
> >>> --
> >>> Jeff Squyres
> >>> jsquyres_at_[hidden]
> >>> For corporate legal information go to:
> >>> http://www.cisco.com/web/about/doing_business/legal/cri/
> >>>
> >>>
> >>> _______________________________________________
> >>> devel mailing list
> >>> devel_at_[hidden]
> >>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
> >>
> >> _______________________________________________
> >> devel mailing list
> >> devel_at_[hidden]
> >> http://www.open-mpi.org/mailman/listinfo.cgi/devel
> >
> >
> > _______________________________________________
> > devel mailing list
> > devel_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
> _______________________________________________
> devel mailing list
> devel_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>

-- 
Jeff Squyres
jsquyres_at_[hidden]
For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/